|
Advanced
Shipboard Communications Demonstrations with ACTS
Roy
A. Axford, Thomas C. Jedrey, Michael A. Rupar
Abstract
For
ships at sea, satellites provide the only option for high
data rate (HDR), long haul communications. Furthermore the
demand for HDR satellite communications (SATCOM) for military
and commercial ships, and other offshore platforms is increasing.
Presently the bulk of this maritime HDR SATCOM connectivity
is provided via C-band and X-band. However, the shipboard
antenna sizes required to achieve a data rate of, say T1
(1.544 Mbps) with present C-/X-band SATCOM systems range
from seven to ten feet in diameter. This limits the classes
of ships to which HDR services can be provided to those
which are large enough to accommodate the massive antennas.
With its high powered K/Ka-band spot beams, the National
Aeronautics and Space AdministrationŐs (NASA) Advanced Communications
Technology Satellite (ACTS) was able to provide T1 and higher
rate services to ships at sea using much smaller shipboard
antennas. This paper discusses three shipboard HDR SATCOM
demonstrations that were conducted with ACTS between 1996
and 1998.
The
first demonstration involved a 2 Mbps link provided to the
seismic survey ship M/V Geco Diamond equipped with a 16-inch
wide, 4.5-inch tall, mechanically steered slotted waveguide
array antenna developed by the Jet Propulsion Laboratory.
In this February 1996 demonstration ACTS allowed supercomputers
ashore to process Geco DiamondŐs voluminous oceanographic
seismic data in near real time. This capability allowed
the ship to adjust its search parameters on a daily basis
based on feedback from the processed data, thereby greatly
increasing survey efficiency.
The
second demonstration was conducted on the US Navy cruiser
USS Princeton (CG 59) with the same antenna used on Geco
Diamond. Princeton conducted a six-month (January-July 1997)
Western Hemisphere solo deployment during which time T1
connectivity via ACTS provided the ship with a range of
valuable tools for operational, administrative and quality-of-life
tasks. In one instance, video teleconferencing (VTC) via
ACTS allowed the ship to provide life-saving emergency medical
aid, assisted by specialists ashore, to a fellow mariner
- the Master of a Greek cargo ship.
The
third demonstration set what is believed to be the all-time
SATCOM data rate record to a ship at sea, 45 Mbps in October
1998. This Lake Michigan (Chicago area) demonstration employed
one of ACTSŐ fixed beams and involved the smallest of the
three vessels, the 45-foot Bayliner M/V Entropy equipped
with a modified commercial-off-the-shelf one-meter antenna.
A variety of multi-media services were provided to Entropy
through a stressing range of sea states. These three demonstrations
provided a preview of the capabilities that could be provided
to future mariners on a more routine basis when K/Ka-band
SATCOM systems are widely deployed.
|
